Transformer clamp



Oct. 23, 1951 H. EPSTEIN TRANSFORMER CLAMP F iled Feb. 24, 1947 n W e m m TD. 0 ME H A wh .H H

Patented Oct. 23, 1951 TRANSFORMER CLAMP Hirsch Epstein, Chicago, Ill., assignor of one-half to Louis B. Duman, Chicago, 111.

Application February 24, 1947, Serial No. 730,630

1 Claim.

This application is a continuation in part of .my pending application Serial No. 567,542, filed December 11, 1944, which is now abandoned.

The present invention relates to transformers or reactors and more particularly such as are used in connection with alternating current hot cathode fluorescent lighting devices.

It is one of the objects of the present invention to provide a reactor or transformer which will operate as noiselessly as possible. 7

The core of the transformers of the above mentioned type generally consists of a series of thin laminations, of substantially L shape, laid to form a rectangular core. I have found that the end laminations are primarily responsible for the transformer noises. Various means have been suggested heretofore for clamping the laminations together to reduce the permissible vibration and thus reduce the noise. Insofar as I am aware the various means provided for noise reduction have been either costly or unsatisfactory. I have discovered that a simple soft iron clamp, of a generally C shape, positioned to embrace and hold the opposite sides of the core at the free or vibrating end of the outermost laminations can be used to prevent vibration of the lamination and thus substantially reduce or entirely eliminate transformer noises.

It is an object of the present invention to provide a simple and inexpensive clamping arrangement for holding the ends of the transformer laminations together and thus reduce the noise making tendency of the transformer. It is a further object of the present invention to provide a clamp which is particularly adapted to hold together the adjacent ends of the two laminations constituting the outermost laminations of the core and thus to prevent those ends from vibrating. It is a still further object of the present invention to provide an improved means for assembling and fabricating the noise reducing clamp at the end of the transformer.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming apart thereof.

In the drawing:

Figure'l is a top view of a transformer, partly broken away, illustrating the present invention; Figure 2 is a fragmentary sectional view taken along the line 2-4 of Figure 1;

Figure 3 is an enlarged fragmentary sectional view taken along the line 3-3 of Figure 1 and illustrating also the condition of the clamp as it is being die formed;

Figure 4 is an elevational view of the dies in Which the clamp is being pressed into position;

Figure 5 is a plan view of the structure of Figure 4 and showing the transformer in position;

Figures 6 and 7 are views corresponding to Figures 4 and 5 and showing an alternate die arrangement;

Figure 8 is a view corresponding to the end of Figure l and showing a transformer with a clamp fabricated in accordance with the process of Figures 6 and 7;

Figure 9 is a sectional view taken along the line 9-9 of Figure 8; and

Figure 10 is a fragmentary view of the end of a transformer showing another clamping arrangement.

Reference may now be had more particularly to the drawing wherein like reference numerals designate like parts throughout.

In Figure l I have shown my invention as applied to a standard type transformer such as is used in connection with fluorescent lighting devices. The transformer I comprises a plurality of individually wound coils 2, Which may be of identical or different characteristics. Each coil is wound on a cardboard or other stiff paper spool 6. A laminated iron core structure I is assembled through the spools 6 of the coils. This core structure comprises a series of identical L-shaped silicon'steel laminations as is usual in the art. Each lamination includes a long leg I2 which extends longitudinally of the finished transformer through a set of coils, and a short leg 13 which extends laterally of the transformer. The laminations are assembled to form a rectangular core in which the long leg [2 of each lamination extends the full length of the core,

whereas the short leg l3 terminates at a line I4. The lateral leg of each lamination is of a length less than the width of the transformer. The laminations are laid in layers so that the meeting edges M of the two laminations of the same layer are on diagonally opposite sides of the core and so arranged that in adjacent layers the meeting edges H are on opposite diagonals of the rectangular core. Each lamination consists of a silicon steel strip approximately 4 of an inch thick. After the core has been assembled it is locked in place by longitudinally extending wooden wedges 18-49 which are tapered at one end, as indicated at 20, and are forced through the coils between the top lamination and the tubes 6. The wedges thus hold the laminations tightly clamped together along the longitudinal sides of the transformer.

It is to be noted that the free lateral ends of the lateral legs l3 of the two top and the two bottom laminations are not locked in place by the wedges l9-l9. The ends of those legs [3 will therefore tend to vibrate and produce transformer noises unless means is provided to prevent this. In order to prevent vibration of the lateral ends of the upper and lower outermost laminations I provide at each end of 'the transformer a C-shaped or channel-shaped clamp of soft steel or iron which is dead, that is, substantially devoid of springiness. The bight portion 26 of each clamp 25 is spaced :from the core. The arms 21-48 bear against opposite lateral faces of the transformer and-may, optionally, be spaced from those faces by a sheet or" paper to prevent the establishment of armagnetic path between the uppermost and the lowermost lamination. The sheet of paper maybe omitted because generally there is enough of a :film .of oxide onthe lamination of the magnetic 'core and on the :surfaces of the arms Zi' and .28 vof :the clamp :to prevent any serious "eddy :current actiondeveloping. The C-shaped'clamp 25 is splacedon the transformer and then the ;arms 21-23 are firmly pressed towards one another as in a pneumatic or hand press. This holds the C-clamp in'position. Thereafter the .end of the transformer maybe wound with a paper strip in the usual manner to provide for the terminals of the wires of the transformer :coils. "The transformer is then coated with an insulating varnish and placed in a container and completely encased by an insulating com- "pound, such-as tar, withinthe container, as is usual in the art, and shown in my application above referred-to.

In'FiguresA-and 5I have shown a die arrangement such as is used for securing the clamp 2-5 in place. This clamping'arrangement includes a pair of relatively movable dies 39 and Gt of a manual or pneumatic press of whichboth dies may be movable towards one another or one may be stationary. The-die 40 includes a die head' l l' having a'pair of'space'd apartears 4242 between which'is pivotally-mounted a die block 2 3 as by apivot pin'fl l. The die block 33 is free to turn through *a'limited angle about the longitudinal axisof-the pin 44. Below the ears 42 thedie head H 'has secured thereto a gauge plate 46 which 'is-adjustably secured to the die head at any desired distance below the cars 42. 'The gauge plate has at the rear thereof anupstanding gauge stop pin 4-1. The working surface of the die block' 43 is concave, as indicated at "flBr'beingcurvedon-such a radius that thedepth of the concavity, for the width of the the block, is approximately half the thickness of the metal-of theclamp 2'5. Thedie it has adieblock 50 in line-with the die block 53 and having a concave working face 5| similar'tothe concave Working face 48. 7

An explanation will 'nowbe given of the manner of securing the clamp 25 in place. The opposite arms of theclamp 25 are initially'spaced apart -an amount sufficient to permit'them to embrace a stack of laminations between the wedges I8'|9. At this time the thickness of the stack of laminations is somewhat "greater than will betheir ultimate-thickness after compression. Ther-eafter the end of the stack of laminations is placed on the gauge plate it and in engagement with the'gauge-stop pin 4?. This accurately positions the stack of laminations with respect to the dies 4350."The two die heads '3940 are then brought together under illustrated in Figure 10.

great pressure. The concave surfaces 48-5l engage the opposite arms 21-48 of the clamp 25 and force them together, deforming the metal of the clamp beyond its elastic limit. The fact that the die block 43 is pivoted assures a proper equalization of force at the opposite edges of each die block. The pressure of the dies on the clamp not only deformsthe clamp :but also compresses the stack of laminations so that upon removal from the die the stack of laminations "are compressed by and exert an outward pressure againstxthe arms 21-28 of the clamp.

Figure 3 shows an enlarged view of the face 48 of the-dieblock 43. In this instance the block as seen in'Figure 3 is inch wide and has at eachwend thereof aflat surface 60 which is apholds the edges"St and-'61:against vibration. It

is at those edges where the 'maximum'yibration would otherwise take place and'wherethemaximum noise would be produced.

'In i igures '6 and '7 1 haveshown a structure somewhat .differentfrom that of Figures 5 and 6,

for accomplishing similar results. *In'this-case the relatively movable die heads are indicated at '69 and 10. A die block'Tl is rigid with respect to the die head 69, anda die' block -12 is pivoted between a pair of cars l3 in the diehead 70 as by a pivot pin 14. ii-pair ofplunger pins 1515 are rigidly mounted in the die block H and a similar pair -of-pins 15-45 are rigidly mountedinthedie block 1-2 which ispivoted' to the die'head 10. Each of the-pins 15 terminates in-a conical-point. These points deform the arms '2 'l28 of -the-c'l'amp 25 and produce'in eacharm a pair of protuberances which are in 'intimate pressure engagement-with the outermost laminations. The-points-of thepins l5-are conical-or spherical. "There is sufiicient give in themetal of the clamp so thatthe 'protuberances-on the inner surfaceso'f the arms'-2l 28, Which-engage the stack of laminations, are of a generally spherical shape and of a comparatively large radius. The protuberances overlie the transformer on both'sides of -the'jline' l4, and-cl'arnp the stack cit-laminations together. In view of the factthat the protuberances overlie the line H on one side of the longitudinalcenter line-of the transformer'and there are similar protuber ances similarly located --on the opposite side of the longitudinal center-line of the -clamp, the

outer laminations'o'f'the "core-are thus positively kept irom vibrating.

The dies of either Figures 4 and 5 orFigures 6 and 7 may be used in connection'withaso'mewhat' overheight clamp to advantage. This is In Figure 10 *there-is shown in dottedlines an overheight clampwhich is to be deformed tohold a'stack of-lan'iinations together. 50' includes a backing support BE'thatbackSthe clamp for half the "height of the clamp. The

movable die block 43' includes a stop 86 that In this instance the non-pivoted die engages the edge 81 of the clamp and holds it against movement inwardly towards the transformer coils. As the die 43' moves towards the die 50' and forces the end 21 of the arm of the clamp towards the stack of laminations' it causes the metal at 88 to bulge away from the core and produce a bulge 89. The metal along the curved portion 90 is deformed in such a manner that any straining tendency is in a direction such as to tend to cause the metal at 9| to move towards the transformer core rather than away from it, so that the bulge 89 constitutes material tending constantly to press the arm 21 towards the stack of laminations. The clamp of Figure 10 may therefore be made of spring metal instead of dead metal if desired.

In compliance with the requirements of the patent statues I have here shown and described a few preferred embodiments of my invention. It is, however, to be understood that the invention is not limited to the precise constructions here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

Alternating current apparatus comprising a laminated core, and soft iron clamping straps extending across the laminations and embracing the lateral sides of the core from an outermost lamination on one side of the stack to the outermost lamination on the opposite side of the'stack and exerting pressure against the stack for clamping the laminations of the stack together, each clamping strap having a pair of arms having concentrated pressure areas adjacent opposite edges thereof and each clamp having an intermediate portion adjoining the said arms thereof, there being substantially a U-shaped bend in the metal of the clamping strap at the juncture between the intermediate portion and one of the arms and with the open side of the U facing the space between the arms.

HIRSCH EPS'I'EIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 14,113 Thordarson Apr. 18, 1916 1,452,939 Sparks et al Apr. 24, 1923 1,480,604 Dubilier Jan. 15, 1924 1,571,501 Van Deventer Feb. 2, 1926 1,587,696 Carter June 8, 1926 1,629,132 'I'hordarson May 17, 1927 1,666,661 Morton Apr. 17, 1928 1,726,100 Da Costa Aug. 27, 1929 2,068,320 Grant Jan. 19, 1937 2,137,883 Ross Nov. 22, 1938 2,176,116 Baetzhold et al. Oct. 17, 1939 2,229,413 Joost Jan. 21, 1941 2,241,261 Horn May 6, 1941 2,262,791 Bransford et a1. Nov. 18, 1941 2,319,775 Mittermaier May 18, 1942 2,320,383 Pepe June 1, 1943 2,328,228 Pearson Aug. 31, 1943 2,350,530 Pickard June 6, 1944 2,393,439 White et al Jan. 22, 1946 2,472,150 Epstein June 7, 1949 

